Electric transmitter



July 10, 1962 w LAV|ANA ET AL 3,043,922

ELECTRIC TRANSMITTER Filed May 5, 1960 36 INVENTORS non/nu w. uvmm 44 WILUAH'E. FRITZ JAMES R. CASS/1N0 avmraiw THEIR ATTORNEY United States Patent .390433922 ELECTRIC TRANSMITTER Donald W. Laviana, Pittsford, and William E. Fritz and James R'. Ca'ssano, Rochester, N.Y., assignors to General Motors Corporation, Detroit, Micln, a corporation of Delaware 4 Filed May 5, 1960, Ser. No. 27,064 Claims. (Cl. 200- 24) This invention pertains to electric inverters, and particularly to an improved transmitter assembly for converting direct current to threephase alternating current.

In copending application Serial No. 2357,9112, filed December 3, 1959, in the name of William E. Fritz et 'al. and assigned to the assignee of this invention, an electric speedometer drive is disclosed including a transmitter and a receiver. The transmitter converts direct current to three phase alternating current having a frequency proportional to vehicle speed. The alternating current signal developed by the transmitter is used to excite the phase windings of a receiver having a rotor which is driven at a-spe'ed directly proportional to the frequency of the alternating current signal. The present invention relates to an improved transmitter construction for use in an electric speedometer drive of the aforesaid type. Accordingly, among our objects are the provision of an improved transmitter construction for converting direct current to three phase alternating current; the further provision of a transmitter including animproved brush drum and means for imparting rotation thereto; and the still further provision of a transmitter including an improved contact assembly wherein the commutator segments are mechanically interlocked with the dielectric material.

The aforementioned and other objects are accomplished in the present invention by designing the brush drum so that the brushes project from only one side thereof for engagement with 'the commutator segments and the power supply slip rings. Specifically, the improved transmitter comprises a housing having a cupshaped recess therein coaxial with a shaft receiving bore. A drive shaft is: supported by a bushing in the bore, the drive shaft being attached to a drive plate disposed within the cup-shaped recess. The brush drum is molded of an insulating material, such as phenolic, and has a pair of notches adapted to receive tangs on the drive plate for coupling the drive plate to the brush drum. In addition, the brush drum is formed with a cylindrical recess for receiving the end of the drive shaft whereby the brush drum is coaxially arranged with respect -to the drive shaft.

The brush drum is molded with eight brush receiving pockets, or recesses, arranged in pairs, each pair being connected by a groove. Each pocket receives a spring and a brush, each pair of brushes being connected by a suitable jumper disposed in the slot between each pocket of each pair.

The contact assembly comprises a disc of molded insulating material having an axially extending annular flange, the slip rings and commutator segments being molded in situ with the insulating material. Accordingly, the commutator segments have a plurality of hooks which are mechanically interlocked with the dielectric material. The spaces between the arcuate commutator segments, and between the segments and the slip rings are filled with an insulating material.

When the contact assembly is assembled with the housing, the outer slip ring engages the housing and thus completes an electrical ground connection. The three commutator segments and the center slip ring are connected to terminals disposed within the annular flange of the commutator body. The disc is held in assembled Patented July 10, 1962 2 relation with the housing by a ring, the end of which is spun over the end of the housing.

Fin't herobjects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown. I

In the drawings:

,FIGURE 1 is a longitudinal view, partly in section and partly in elevation, depicting the improved transmitter construction.

FIGURES 2 and 3 are sectional views taken along lines 2 2 and 3-3, respectively, of FIGURE 1.

FIGURE 4 is a fragmentary sectional view taken along line 44 of FIGURE 3 illustrating one embodiment of a brush jumper. 7

FIGURE 5 is a view similar to FIGURE 4 illustrating a modified form of the brush jumper.

With reference to FIGURES 1 through 3, the transmitter comprises a die cast housing 10 having an externally threaded mounting portion 12, a cup-shaped recess 14 and a through bore 16. The cup-shaped recess 14 is coaxial with the through bore 16, and a bushing 18 is press fitted in the bore 16. A drive shaft 20 is journalled in the bushing 18, the drive shaft having a pinion 22 attached to one end and a drive plate 24 staked at 26 to the other end thereof. An oil seal 23 is disposed between the plate 24 and the inner end of the bushing 18. As clearly seen in FIGURE 1, the plate 24 has a pair of diametrically opposed axially extending tangs 29. g

A brush drum assembly 30 is coaxially arranged within the cup-shaped recess 14. The brush drum assembly 30 comprises a generally H-shaped body of insulating material 32 having notches 34 for receiving the tangs 29 on the driveplate 24. The body 32 is molded with eight axially extending substantially square bushing receiving pockets, or cavities 36 which are arranged in pairs connected by axially extending grooves 38. In addition, the body 32 is formed with a cylindrical recess 40 adapted to receive thereduced diameter end 42 on the shaft 20.

Each pocket 36 receives a coil spring 44 and a brush, the brushes being indicated by numerals 46, 48, 50, 52, 54, 56, 58 and 60. The brushes 46 and 48 constitute one pair, and are connected by either a metallic jumper 62 as indicated in FIGURE 4 or a pigtail jumper 64 as indicated in FIGURE 5. The jumpers 62 or 64 extend through the grooves 38 connecting the pockets of each pair. The other pairs of brushes comprise brushes 50 and 52; 54 and 56; and 58 and 60.

The open end of the cup-shaped recess 14 in the housing 10 is closed by a contact assembly 66 comprising a disc 68 of insulating material having an integral axially projecting annular flange 70. An outer metallic slip ring 72 and three arcuate commutator segments 74, 76 and 78 are molded in situ with the insulating material of the disc 68. The slip ring 72 is formed with three circumferentially spaced hooks 80, and each of the segments 74, 76 and 78 is formed with a pair of circumfereutially spaced hooks 82 which are interlocked with the dielectric material. The molded insulating material comprising the disc 68 completely fills the annular space 84 between the slip rings 72 and the segments 74, 76 and 78, as well as the spaces 86 between the segments and the annular space 88 between the seg ments and the center slip ring 90.

The segments 74, 76 and 78 are formed with integral terminal portions 92, 94 and 96 which extend into the space defined by the annular flange 70. The center slip ring is attached to a central terminal stud 98.

The contact assembly 66 is held in assembled relation with the housing 10 by a ring 100, the end of which is spun over a flange on the housing. A weather seal 102 is interposed between the edge of the contact assembly 66 and the housing 10. The outer slip ring 72 engages the housing 10 and thus completes the ground circuit. The terminal stud 98 is connected to the opposite terminal of a direct current power supply, such as a vehicle battery, and accordingly brushes 54 and 58 which engage the center slip ring 90- and are connected to one terminal of the direct current power supply while brushes 46 and 52 which engage the slip ring 72 are connected to the other terminal of the direct current power supply. Since brush 46 is connected to brush 48, and brush 52 is connected to brush 50, the brushes 48 and 50 are electrically grounded. Moreover, brushes 56 and 60 are connected to the other terminal of the power supply so that upon rotation of the brush drum 30 by the drive plate 24 the direct current supply voltage will be converted to three phase alternating current having a frequency proportional to the rotative speed of the drum assembly 30. The brushes '48 and 50, and 56 and 60 engage successive commutator segments 74, 76 and 78 during relative rotation between the brush drum assembly 30 and the contact assembly 66. Moreover if desired, the specific resistance of the brushes 56 and 60 may vary, as may the specific resistance of the brushes 48 and 50 so that the staircase wave forms derived from the commutator segments approximate sine waves.

While the embodiment of the invention as herein dis-' closed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A transmitter for an electric speedometer drive including, a housing having a cup-shaped recess, a rotatable brush drum assembly coaxially disposed within said recess and having a pair of diametrically opposed radially extending slots, a drive shaft rotatably supported in said housing, a drive plate connected to said drive shaft and having a pair of axially extending tangs snugly received in the notches of said brush drum assembly, a stationary contact assembly attached to said housing having a plurality of circumferentially spaced commuta tor segments, an outer coaxial slip ring and a center coaxial slip ring thereon, first brush means carried by said brush assembly engaging said outer slip ring, second brush means carried by said brush drum assembly engaging said center slip ring, and third brush means car-- ried by said brush drum assembly and engageable with said segments, certain of said third brush means being electrically connected to the first brush means and other of said third brush means being electrically connected to the second brush means.

2. A transmitter for an electric speedometer drive including, a housing having a cup-shaped recess, a rotatable brush drum coaxially disposed within said recess, said brush drum having a plurality of pairs of axially extending polygonal cavities therein and an axially extending groove connecting the cavities of each pair, a drive shaft rotatably supported in said housing and connected to said brush drum, a stationary contact assembly attached to said housing having a plurality of circumferentially spaced commutator segments, an outer coaxial slip ring and a center coaxial slip ring thereon, a spring biased brush slidably mounted within each cavity of said brush drum, and means electrically interconnecting the brushes of each pair.

3. The transmitter set forth in claim 2 wherein the electrical means interconnecting the brushes of each pair comprise a metallic brush jumper disposed within the groove connecting the cavities of each pair.

4. The transmitter set forth in claim 2 wherein the means electrically interconnecting the brushes of each pair comprise a pigtail extending through said groove and having its ends attached to the brushes of each pair.

5. The transmitter set forth in claim 2 wherein the said housing is composed of electrically conductive material, and wherein said outer slip ring is electrically connected thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,166,923 Nee'ley Jan. 4, 1916 2,081,184 Ross et al. May 25, 1937 2,321,805 Fritzinger June 15, 1043 2,518,628 Maclntyre Aug. 15, 1950 2,700,076 Goode Jan. 18, 1955 2,821,584 Monack et al. Jan. 28, 1958 2,852,628 Fry Sept. 16, 1958 

